The α1-selective adrenergic blocking agents have been used for a long time in the treatment of hypertension. The aim of our work was a comparative study between piperazinyl-quinazoline derivatives (prazosin, terazosin, doxazosin), the identification and separation of these substances and the analysis of their degradation products, using modern analitycal chromatographic ( TLC, HPLC-MS) and UV-spectrophotometric methods.